Medical Image Compression Part 1 - Entropy Encoding

There are thousands of different data compression algorithms in existence, many of which you use. Some of the most popular include gzip, JPEG and PNG which are used in almost every web site you visit. You may have also heard of image compression algorithms used in DICOM for medical imaging – specifically JPEG, JPEG-LS, and JPEG 2000. The DICOM standard refers to these image compression algorithms as “Transfer Syntaxes” and each is assigned a unique identifier (or UID). For example, the UID for the JPEG 2000 lossless transfer syntax is 1.2.840.10008.1.2.4.90. The DICOM standard currently supports over 15 different compressed transfer syntaxes and in the past supported another 15 different compressed transfer syntaxes which were not used and retired. You may wonder why there are so many different image compression algorithms and what the difference is between them. That is the focus of this series – to explore the algorithms behind image compression and the associated tradeoffs with a focus on JPEG 2000.